Modem cards allow a computer to wirelessly communicate with a communications system. During operation of the modem card, the modem card transmits wireless signals to the communications system. In some instances, the communications system requests that the PC card increase the transmit power of the signals. The modem card can increase the transmit power up to a maximum transmit power. The maximum transmit power is generally set by the manufacturer of the modem card.
Modem cards are powered by a power supply located in the computer to which the modem card is connected. Increasing the transmit power of the modem card increases the current draw from the modem card. As a result, the increased transmit power can cause a drop in the voltage of the power being supplied to the modem card by the computer (supplied voltage).
Different computer manufacturers use different power supplies. As a result, increasing the transmit power to the maximum transmit power causes the supplied voltage to drop to different levels in different computers. In some computers, the supplied voltage can drop below a shut-down voltage where the computer shuts down the computer or the modem card. As a result, there is a need for modem cards that compensate for variation in the power supplies used in different computers.